Snowy Owl
Retired in 2010, In Memoriam
Bird flu vaccine ?promising?
By HELEN BRANSWELL The Canadian Press
http://thechronicleherald.ca/Canada/527791.html
By HELEN BRANSWELL The Canadian Press
http://thechronicleherald.ca/Canada/527791.html
TORONTO ? A vaccine against H5N1 avian flu made with live but weakened viruses showed considerable promise when tested in animals, even protecting against strains that had mutated or "drifted" significantly from the one contained in the vaccine, U.S. researchers reported Monday.
If human testing produces similar results, it would suggest live-virus influenza vaccines could be made in advance and stored for immediate use once a flu pandemic begins ? giving countries with access to live-virus vaccine a way to begin protecting their citizens months ahead of those dependent on traditional flu shots.
Dr. John Treanor, a vaccine expert at the University of Rochester, N.Y. who was not involved with the work, said the "very promising" findings support the theory that in a pandemic, this type of vaccine could be the most useful available.
"The thing that really makes sense as a vaccine for pandemic flu is a live vaccine," said Treanor, who said the work reported in this study supports that view.
"Everything looks positive, from what she?s showing."
The "she" Treanor referred to is Dr. Kanta Subbarao, an expert in the development of live-virus influenza vaccines. The senior author of the study, Subbarao works at the U.S. National Institute for Allergy and Infectious Diseases.
Some of Subbarao?s co-authors work for MedImmune Inc., an American company which makes live-virus flu vaccine and with which the U.S. National Institutes of Health have partnered on live-virus vaccine research. Funding for the work, which was published in the journal PloS Medicine, was provided by the NIH.
The researchers reported on the creation and testing of live-virus vaccines made with H5N1 viruses collected in 1997, 2003 and 2004. The vaccines were tested in mice and ferrets. The latter are susceptible to human and avian flu viruses and are considered the closest animal surrogate for humans in the study of flu.
The scientists found that one dose of vaccine was sufficient to prevent mice from dying when they were exposed to or "challenged" with an H5N1 virus, even though the mice didn?t develop the types of antibodies generally considered to be proof of immune protection. Two doses of vaccine protected both mice and ferrets from developing illness when they were challenged with H5N1 virus and resulted in good antibody responses.
It is assumed that everyone will need two doses of injectable vaccine to protect against a new strain of influenza to which they?ve never been exposed ? the circumstance of a pandemic. But there has been some thought that rule might not hold true for live-virus vaccine ? a theory these results can?t prove, but don?t contradict either.
On that question Treanor voiced caution, saying it can?t be concluded that results in mice will translate into humans. "You just have to see if it actually works. To do that you need to get to the point where you?re testing these in humans to find out," he said.
The first human testing began in June, at Johns Hopkins University in Baltimore, Md. But Subbarao said the data from that first round of testing ? a small trial designed to study safety only ? aren?t yet ready for publication.
Live-virus vaccines would have a number of attractive advantages during a pandemic. In addition to the idea that they could be stored for early deployment, they require less virus per person, meaning a batch of eggs could produce many more doses of live-virus vaccine than the killed-virus type.
If human testing produces similar results, it would suggest live-virus influenza vaccines could be made in advance and stored for immediate use once a flu pandemic begins ? giving countries with access to live-virus vaccine a way to begin protecting their citizens months ahead of those dependent on traditional flu shots.
Dr. John Treanor, a vaccine expert at the University of Rochester, N.Y. who was not involved with the work, said the "very promising" findings support the theory that in a pandemic, this type of vaccine could be the most useful available.
"The thing that really makes sense as a vaccine for pandemic flu is a live vaccine," said Treanor, who said the work reported in this study supports that view.
"Everything looks positive, from what she?s showing."
The "she" Treanor referred to is Dr. Kanta Subbarao, an expert in the development of live-virus influenza vaccines. The senior author of the study, Subbarao works at the U.S. National Institute for Allergy and Infectious Diseases.
Some of Subbarao?s co-authors work for MedImmune Inc., an American company which makes live-virus flu vaccine and with which the U.S. National Institutes of Health have partnered on live-virus vaccine research. Funding for the work, which was published in the journal PloS Medicine, was provided by the NIH.
The researchers reported on the creation and testing of live-virus vaccines made with H5N1 viruses collected in 1997, 2003 and 2004. The vaccines were tested in mice and ferrets. The latter are susceptible to human and avian flu viruses and are considered the closest animal surrogate for humans in the study of flu.
The scientists found that one dose of vaccine was sufficient to prevent mice from dying when they were exposed to or "challenged" with an H5N1 virus, even though the mice didn?t develop the types of antibodies generally considered to be proof of immune protection. Two doses of vaccine protected both mice and ferrets from developing illness when they were challenged with H5N1 virus and resulted in good antibody responses.
It is assumed that everyone will need two doses of injectable vaccine to protect against a new strain of influenza to which they?ve never been exposed ? the circumstance of a pandemic. But there has been some thought that rule might not hold true for live-virus vaccine ? a theory these results can?t prove, but don?t contradict either.
On that question Treanor voiced caution, saying it can?t be concluded that results in mice will translate into humans. "You just have to see if it actually works. To do that you need to get to the point where you?re testing these in humans to find out," he said.
The first human testing began in June, at Johns Hopkins University in Baltimore, Md. But Subbarao said the data from that first round of testing ? a small trial designed to study safety only ? aren?t yet ready for publication.
Live-virus vaccines would have a number of attractive advantages during a pandemic. In addition to the idea that they could be stored for early deployment, they require less virus per person, meaning a batch of eggs could produce many more doses of live-virus vaccine than the killed-virus type.